Flame stabilizer



June 28, 1960 A. c. SCURLQCK 2,942,419

FLAME STABILIZER Filed Aug. 16, 1955 3 Sheets-Sheet 1 FUEL GAS AND AIR AND AIR.

INVENTOR An! 5. (fall/110015 AGENT June 28, 1960 i A. c. SCURLOCK 2,942,419

FLAME STABILIZER Filed Aug. 16, 1955 3 Sheets-Sheet 2 INVENTOR 4 jg AIM/i 'faw/wk AGENT June 28, 1960 A. c. scuRLocK FLAME STABILIZER 3 Sheets-Sheet 3 Filed Aug. 16, 1955 AGENT United States 1 her.

"loss. l The object of this invention is to provide a means for stabilizing the flame in a high-velocity gas combustion 2,942,419. Patented June 28, 1960 FLAME STABILIZER Arch Chilton Scurlock, Washington, D. C., assignor to Atlantic Research Corporation, Alexandria, Va., a corporation of Virginia Filed Aug. 16, 1955, Ser. No. 528,847

8 Claims. (Cl. 60 --'39.72) V This invention relates to combustion chambers in which combustion must be maintained, in a 'highvelocity gas stream, as,1for example, in the case of turbojet'or ramet combustion chambers, combustion chambers .for in- More specificalas an ignition source by 'virtueof the fact that an eddy region containing hot combustion gases forms downstream of the flame holder and ignites the adjacent unburned gas stream. The flame flares outward down- To maintain flame propagation in the stream of rapidly I stream of the stabilizer to 'form a roughly 'V shaped combustion zone with its apex at the downstream .end

of the stabilizer. Combustion approaches completion when the downstream extremity of this combustion zone extends across the entirewidth of the combustion charm that combustion go substantially to completion before exhaustion, the combustion chamber must be of suflicient length to effectuate this.

Generally speaking, the flame stabilizers are in the form of stationary rods, gutters, vanes and the "like,

positioned in the combustion chamber at a point downstream of the air (or oxygen) and fuel intake. "Where a single flame holder is employed, the flaring sides of the flame extend for a considerable distance before the walls of the combustion chamber are reached and combustion is complete. This requires a combustion chamber length which, for many purposes, is excessive both in terms of size and weight. To overcome this difliculty, it has often been the practice to employ a plurality of stationary flame holders since, in such case, the flames flaring from each of the flame "holders soon intersect with each other and the side walls of the chamber and thus make possible the use of a shorter combustion chamber.

The use of a plurality of flame stabilizers, however,

possesses a serious disadvantage. A stabilizer positioned in the vflow stream of high-velocity gases causes a frictional pressure drop which reduces efiiciency and, which therefore, for optimum performance should be kept as 'loW as possible. plurality of flame holders, while making possiblea reduction in chamber length, multiplies frictional pressure chamber which makes possiblea large reductionfin chamber length with minimum frictional pressure loss.

Other objects and advantages of my invention will beand the drawings.

Since, for efliciency of'operation, it is desirable Unfortunately the introduction of 'a' In the drawings:

Figure 1 is a schematic perspective view of a combustion chamber showing the flame fronts formed with a stationary flame holder.

Figure 2 is a schematic perspective view of a combustion chamber showing the flame fronts formed with a rotating flame holder.

Figure 3 is .aischematic perspective view of a'combustion chamber equipped with a centrally mounted, rotating transverse rod stabilizer.

Figure 4 is a schematic perspective view of a combustion chamber equipped with a centrally mounted, rotating gutter-type flame holder.

Figures 5-7 are schematic perspective views of combustion chambers equipped with rotating flame holders which are still other embodiments of my invention.

Figure 8 is a schematic perspective view of a combustion chamber showing :an oscillating flame holder.

1 have found that when a flame stabilizer is moved in the combustion chamber in such a way that it sweeps substantially transversely across the path or axis of gas flow, 'theflame front is generated at a much higher rate than that obtained when the stabilizer is stationary. The moving stabilizer causes the gases to burn not only in a substantially longitudinal direction but also transversely with the result that combustion is completed in a con- 'siderably smaller chamber volume then would be required if the stabilizer were stationary.

Figures 1 and '2 respectively illustrate diagrammatically the flame fronts generated by a stationary open-end gutter-type flame holder and those generated by the .same

stabilizer when it is moved across the path of gas flow by rotating it about the central longitudinal axis of the length relative to width since combustion is substantially complete only when the flame front reaches the side walls. In Figure 2, the rotating stabilizer 4 continuously sweepsacross unburned portions of the downstreaming gases and, as it moves, serves as an ignition pilot so that the flame front 5 .is generated with greater rapidity. The'flame propagates both longitudinally and transversely, assuming a convoluted or helical shape, as shown, with substantially complete combustion of the gas in a considerably smaller chamber volume than that required in Figure 1. Thus the length of chamber A required for substantially complete combustion where the stabilizer sweeps across gas flow is very considerably less than that required with the stationary flame holder of Figure 1.

To achieve the transverse sweeping of the flame holder across the path of fuel gas flow requisite to obtain the desired rapid transverse propagation of the flame, the flame holder must be independent of, freely movable relative-to, and spaced downstream from the fuel gas source,

1 as shown in the figures.

A single moving flame holder accomplishes what has hitherto required the use of a plurality of stationary stabilizers with the additional important advantage'that it maintains frictional pressure loss at a minimum, the pressure drop in thedirection of flow being substantia'lly the same as that produced by a single stationary fiame stabilizer of the same shape and size. The more rapid the motion of the flame holder, the more rapid is generation of the flame front, the higher is heat release per unit of combustion chamber volume, and the shorter "ishthe length of combustion chamber required for complete combustion of the gases. For most efficient operation,

of fuel, the velocity of gas intake, the desired rate of heat release, and thelike.

The stabilizer can be of any suitable shape or size and can be moved in any desired manner as long as it is so designed or positioned that it sweeps across the path of gas flow. It can, for example, be rotated about the cen-.

tral axis of the combustion chamber. This type of motion is particularly suitable for use in a cylindrical combustion chamber.

The rotating flame holder can be centrally positioned in the combustion chamber or at any point peripheral to the central, longitudinal axis of the chamber. If it is placed at the central axis of the chamber, as shown, for example, in Figure 2, the flame holder should be of a shape such that its transverse axes are substantially different in length. In other words, the length and width dimensions of the stabilizer in the plane transverse to the combustion chamber should be different, as shown in Figure 2, so that, as it rotates, the stabilizer sweeps across the downstreaming gases, thus providing ignition substantially from the center to the periphery of the chamber. Examples of flame holders which meet this requirement include, for example, transverse rod, openand closed-end gutter and vane-type stabilizers, as shown in Figures 2, 3, 4 and 7.

A rotating stabilizer can also be positioned at any point peripherally of the central axis of the combustion chamber. This can be at a point, for example, which is spaced between the central axis and the-side. walls or which is adjacent to or attached to a rotating section of the sidewalls of the combustion chamber. Where the stabilizer is positioned peripherally of the central axis of the chamber, it is rotated by suitable means about the central axis thus sweeping across the path of gas flow. It is, therefore, not essential, as in the case of the centrally positioned stabilizer, that the stabilizer have transverse axes which are of different dimensions. Thus, in addition to rod, gutter and vane shaped stabilizers, spherical or conical flame holders can be employed.

Rotation of the stabilizer can be effected by any desired means as, for example, by attachment to a small propeller in the approach flow, by means of a powered shaft coming in from the upstream end, by rotation of a short section of the combustion chamber wall to which the stabilizer is firmly attached, and the like.

The flame holder can also be moved to and fro in .reciprocatory or oscillatory fashion substantially transversely across the axis of gas flow. This is especially satisfactory in the case of a rectangularly-shaped combustion chamber. A stabilizer of any desired shape or size can be employed in this manner.

The flame holder should, of course, be designed to meet the particular conditions of use, in terms, for example, of size. Generally speaking, the higher the velocity of the gases, the larger should be the stabilizer to prevent blow-ofl. In this respect, the moving stabilizer possesses the important advantage of adjustability to a considerable range of gas velocity since, at increased intake gas velocities, blow-off can, in some instances, be avoided by reducing the speed of the stabilizer.

To further increase flame stability, it may be desirable in some cases where a rotating stabilizer is utilized to make the flame holder wider or larger at points where the velocity of the stabilizer relative to that of the unburned gases is greatest. In the case of a centrally positioned rotating flame holder, for example, this can be accomplished by making the peripheral ends of the stabilizer wider or somewhat larger than the central portion.

To obtain maximum flame stability, it is desirable, though not essential, to design a rotating stabilizer in such a way as to maintain maximum bluffness in the direction of gas flow across it, namely in the downstream direction of the gases which are given a rotational vector by the sweep of the stabilizer across them. Where the stabilizer is spherical or cylindrical, as in the case of a transversely positioned rod, no adjustment is required because of the symmetry in the direction of gas flow. In the case of flame holders where the point of maximum bluffness is not in such symmetrical relationship to the leading upstream edge, it may be desirable to orient the flame holder in such a way that it produces maximum flame stability. A gutter-type, centrally mounted flame holder, for example, can be twisted in opposite directions peripherally from the center mounting, as shown in Figures 4 and 7, so that each arm of the rotating flame holder presents a leading edge which is substantially parallel to the axis of gas flow and flares to maximum blutfness substantially in the direction of flow of the gases across the stabilizer.

Figure 3 shows a centrally mounted, transverse rod stabilizer 6 which is rotated by means of a small propeller 7 situated in the unburned gases upstream of the flame holder and integrally attached to the stabilizer by rod 8.

Figure 4 shows a centrally mounted gutter-type flame holder 9 shaped so that the opposite arms are oriented for maximum flame stability in the direction of the gas flow which is given a rotational vector by rotation of the stabilizer. In this case rotation of the flame holder is accomplished by an upstream, integrally attached, rotating shaft -10 powered by a motor 19 through drive shaft 20 and bevel gears 21 and 22.

Figure 5 shows a spherical flame holder 11, positioned between the central axis of the combustion chamber and the outside walls, which is rotated about the central axis as shown, by means of an integrally attached upstream rotating shaft 12 powered by conventional means not shown.

Figure 6 shows a flame holder which is similar to that illustrated in Figure 5 but positioned adjacent the side walls of the combustion chamber. The side walls are provided with groove 13 in which the stabilizer moves.

Figure 7 shows a gutter-type flame holder 14 attached at the ends to a rotating collar 15 driven by conventional means as shown. The stabilizer projects across the chamber so that as the collar is rotated, it sweeps across the path of the downstreaming gases.

Figure 8 shows a transverse rod flame holder 16 which is oscillated to and fro across the rectangular combustion chamber 17 by means of a vibrating spring 18 vibrated by conventional means not shown.

Although this invention has been described with reference to illustrative embodiments thereof, it will be apparent to those skilled in the art that it can be embodied in other forms within the scope of the appended claims.

I claim:

1. A combustion chamber, a source of fuel gases and oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstream of said source of said gases and in the path of flow of said fuel and oxygencontaining gases, said flame holder being independent of and freely movable relative to said source of said gases, and means associated with said flame holder for continuously moving said flame holder substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by its transverse motion across the path of said fuel gases, to generate a substantially larger flame front within a given combustion chamber volumethan would be generated if said flame holder were stationary with respect to the path of flow of said gases.

2. A combustion chamber, a source of fuel gases and oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstreamof said source of said gases and in the path of flow of said fuel and oxygencontaining gases, said flame holder being independent of and freely movable relative to said source of said gases,

7 and means associated withtsaid flame holder for continuously oscillating said flame holder substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by its transverse motion across the path of said fuel gases, to generate a substantially larger flame front within a given combustion chamber volume than would be generated if said flame holder were stationary with respect to the path of flow of said gases.

3. A combustion chamber, a source of fuel gases and oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstream of said source of said gases and in the path of flow of said fuel and oxygencontaining gases, said flame holder being independent of and freely movable relative to said source of said gases, and means associated with said flame holder for continuously rotating said flame holder about the central,

rotating it about the central, longitudinal axis of the combustion'chamber and substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by.its transverse motion across the path of said fuel gases, to generate a substantially'larger flame front within a given combustion chamber volume than would be generated if said flame holder were stationary with respect to the path of flow of said gases.

6. A combustion chamber, a source of fuel gases and of oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstream of said source of said gases, in the path of flow of said fuel and oxygencontaining gases, adjacent to the walls of the combustion chamber, and peripherally spaced from the central, longitudinal axis of the combustion chamber, said flame holder being independent of and freely movable relative to said source of said gases, and means associated with said flame holder for continuously rotating it about the central, longitudinal axis of the combustion chamber and substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by its transverse motion across the path of said fuel gases, to generate a substantially larger flame front within a given combustion chamber volume than would be generated longitudinal axis of the combustion chamber and substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by its transverse motion across the path of said fuel gases, to generate a substantially larger flame front within a given combustion chamber volume than would be generated if said flame holder were stationary with respect to the path of flow of said gases.

4. A combustion chamber, a source of fuel gases and oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstream of said source of said gases in the path of flow of said fuel and oxygencontaining gases, said flame holder being independent of and freely movable relative to said source of said gases, and having dimensions of substantially different lengths in a plane transverse to the longitudinal axis of the combustion chamber, and means associated with said flame holder for continuously rotating it about the central, longitudinal axis of the combustion chamber and substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by its transverse motion across the path of said fuel gases, to generate a substantially larger flame front within a given combustion chamber volume than would be generated if said flame holder were stationary with respect to the path of flow of said gases.

5. A combustion chamber,,a source of fuel gases and of oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstream of said source of gases, in the path of flow of said fuel and oxygen-' if said flame holder were stationary with respect to the path of flow ofsaid gases.

7. A combustion chamber, a source of fuel gases and of oxygen-containing gases for injection of said gases into said combustion chamber, a gutter type flame holder positioned in said combustion chamber downstream of said source of said gases, in the path of flow of said fuel and oxygen-containing gases, and centrally mounted at the central, longitudinal axis of the combustion chamber, each of the arms peripherally from the center of the flame holder presenting an upstream edge which is substantially parallel to the direction of gas flow across the flame holder and flaring downstream to maximum bluffness substantially in the direction of flow of the gases across the flame holder, said flame holder being independent of and freely movable relative to said source of said gases, and means associated with said flame holder for continuously rotating it about the central, longitudinal axis of the combustion chamber and substantially transversely across said path of fuel gas and oxygen-containing gas flow during said gas flow, the flame holder throughout said motion being in flame stabilizing position, and functioning solely to stabilize the flame produced by combustion of said fuel gases and, by its transverse motion across the path of said fuel gases, to generate a substantially larger flame front within a given combustion chamber volume than would be generated if said flame holder were stationary with respect to the path of flow of said gases.

8. A combustion chamber, a source of fuel gases-and of oxygen-containing gases for injection of said gases into said combustion chamber, a flame holder positioned in said combustion chamber downstream of said source of said gases, in the path of flow of said fuel and oxygencontaining gases, and attached to a collar rotatably mounted on the wall of the combustion chamber peripheral to the central, longitudinal axis of the combustion chamber and extending interiorly into the combustion chamber, said flame holder being independent of and freely movable relative to said source of said gases, and means associated with said collar for continuously rotating the collar and flame holder attached thereto about the central, longitudinal axis of the combustion chamber and substantially transversely across said path of fuel gas References Cited in the file of this patent UNITED STATES PATENTS Cleveland II May 3, 1955 Karlby et al. Mar. 12, 1957 Spalding Feb. 18, 1958 FOREIGN PATENTS Canada Mar. 1, 1955 wp-m 

